1. Field of the Invention
This invention relates to a vertical band saw machine, more particularly to a vertical band saw machine having an endless band saw blade that is convenient to replace.
2. Description of the Related Art
Referring to FIG. 1, a conventional vertical band saw machine 10 is shown to include a base 12 with a worktable 16 for supporting a workpiece (not shown), a coupling unit 11 which includes a lower coupler 111 secured to the base 12, an upper coupler 112, and a spacer 113 interposed between the lower and upper couplers 111,112 and secured together by means of a screw fastener 114, a mounting frame 13 secured to the upper coupler 112, upper and lower blade mounting pulleys 15,14 rotatably mounted on the mounting frame 13 and the base 12, and an endless band saw blade 17 trained on the pulleys 15,14 and passing through the worktable 16. When it is desired to replace the band saw blade 17, the screw fastener 114 is first loosened to permit removal of the spacer 113 so as to shorten the distance between the pulleys 15,14 for facilitating removal of the band saw blade 17. Subsequently, a new saw blade 17 is then trained on the pulleys 15,14. The spacer 113 is again mounted between the upper and lower couplers 112,111, and is secured by tightening the screw fastener 114. Therefore, the replacement of the band saw blade 17 as such is relatively inconvenient to conduct. Besides, the construction of the coupling unit 11 can be used only for a predetermined size of the band saw blade 17. Moreover, the coupling unit 11 does not provide tension adjusting means for appropriately adjusting the tension of the band saw blade 17 to maintain good sawing quality after a period of use.